Map for sort fields (local to remote).

<div class="definition">
    Object, default = {}
</div>

By default, if you click on the column, it will add column field to the sortData array to send to the server side for sorting.
However, sometimes column field names are not the same as sort names. The <span class="property">.sortMap</span> allows to map sort
fields differently.
<div style="height: 10px"></div>

You can defined it during object creation:
<textarea class="javascript">
let grid = new w2grid({
    name : 'grid',
    url  : 'url/to/server',
    columns: [
        { field: 'recid', text: 'ID', size: '50px' },
        { field: 'lname', text: 'Last Name', size: '30%' },
        { field: 'fname', text: 'First Name', size: '30%' },
        { field: 'email', text: 'Email', size: '40%' },
        { field: 'sdate', text: 'End Date', size: '120px' }
    ],
    sortMap: {
        lname : 'lastName',
        fname : 'firstName'
    }
});
</textarea>

Or any time during the run-time:
<textarea class="javascript">
w2ui.grid.sortMap['email'] = 'main.email';
</textarea>